my doubt is , can i opt for a binacular core instead of two ferrite beads glued togather in parallel manner ?iam using these cores for building inductor.will the inductance value change when i use binacular core (for same turns as in ferrite beads)?

Part of being an engineer or a tech is figuring out how to make less than ideal parts work in the real world. Many (if not most) an exact match is not needed, all you have to do is look at what the stressors are going to be, and make sure the part can handle it.

I built Bertus' amplifier but used an IRF-510 instead of the IRF-840. It seemed to work fine after a little tweaking. If you can't find the exact parts, I would recommend breadboarding the circuit first so you can experiment with part substitutions without having to do alot of soldering and de-soldering. Using a breadboard or free-style soldering can help you with your experiments.